Going all the way back to ancient Egypt, the plumb bob has been one of the most reliable tools in construction. This pointed metal weight, attached to a line, uses gravity to establish a true vertical reference line. Builders, carpenters and surveyors use this tool to make walls, columns and door frames, and to accurately transfer points from high positions to the ground.
This example of a plumb bob was made of brass by General Hardware Manufacturing Co. Dating to the 1950s, it is marked “No 800 16oz” and is part of the George Proctor collection.
The reason you rarely see them used now is that lasers have largely replaced plumb bobs in today’s construction industry.